In my own terms, there is both qualitative and quantitative knowledge. The former would relate, most importently, to knowledge about how to live and why. The latter would be things like State Capitals, and the use of algorithyms.
I think one could posit a best practice for the communication of the latter, although even there some variation would be needed, but with respect to the former, literally an infinite repertoire of tactics of communication might be needed.
Ultimately, happiness and contentment are immanent: they are the emergent properties of a system in motion–an individual personality–that has reached a qualitative state in which those outcomes are common and even perennial. Since they are not tangible, since can’t touch them, it is difficult to communicate how those states were reached. You can say “I think this way”, and “I act this way”, but as religious teachers throughout the ages have found, that is often not enough, and quite often words have a way of causing people to be ignorant with confidence. Wars have often been fought between religions of “peace”. This is the result not of religion, per se, but of human stupidity.
Hindus have this concept of “darshana”, Sufis of Barakah, Jews of Berakhah, and Christians of grace, where simply being in the presence of someone who is spiritually advanced helps one advance. I have never met anyone I can recall who I really feel helped me (nor have I spent much time pursuing them, although I would really enjoy meeting Doris Lessing), but–and if this sounds like wishy-washy pseudo-mystical California bullshit, so be it–I have seen such people in my dreams. I have SEEN Windhorse, felt it. I have met angels, and however people want to psychoanalyze it, the experiences were life-changing. Not life-shaking, but they have had a subtle salutary effect on me.
It is a truism that children tend to become how you are, not how you talk, and that is an excellent example of the verity of the principle of qualitative communication.
Zen, by the way, is an explicit philosophy based on the idea that there are some things worthy knowing, that cannot be said.